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Main Boards => PowWow => Topic started by: Bob B. on February 29, 2012, 05:40:00 PM

Title: Stored energy calculation
Post by: Bob B. on February 29, 2012, 05:40:00 PM
I am currently working with the physics department in our high school and am attempting to create a lab that will calculate the efficincy of levers.  Naturally, I am thinking of bow limbs as the levers and the arrow the load.

I am having trouble finding a simple way to calculate stored energy so we can find Dynamic efficiency.

Any ideas out there?

Bob.
Title: Re: Stored energy calculation
Post by: tradlongbow on February 29, 2012, 05:43:00 PM
Bob-

Contact Stu Miller, I bet he can help.
hkg3sg1@sbcglobal.net

Darren
Title: Re: Stored energy calculation
Post by: khardrunner on February 29, 2012, 05:58:00 PM
If you are thinking specifically of a bow you can use the draw weight as elastic PE. Some conversion would be needed to get it into newtons from pounds, but a quick google search should rectify that.
Title: Re: Stored energy calculation
Post by: wingnut on February 29, 2012, 06:33:00 PM
Bob,

Measure accurately the draw weight at each inch from brace to 28 inches.  Plot them on a graph and solve for the area under the graph.  There are some accurizing steps to smooth the graph lines but I think you get the idea.

That's will be the stored energy.

Mike
Title: Re: Stored energy calculation
Post by: cbCrow on March 01, 2012, 07:41:00 AM
If you go to the A&H archery site to knowledge base they have a very good explanation of how to determine and I bet if you get in touch with them you might get some help with your project.
Title: Re: Stored energy calculation
Post by: moebow on March 01, 2012, 07:51:00 AM
There is a book out there called "Archery the Technical Side."  It is a collection of articles all about the physics of archery.  C N Hickman, Paul Klopsteg and Forest Nagler are three of the authors.  These writers did this back in (I think) the 1930s but the science hasn't changed.

If you can find that book, it will answer many questions and show the math involved.
Title: Re: Stored energy calculation
Post by: Bob B. on March 01, 2012, 08:37:00 AM
I appreciate the info fellas .. I have a good place to start.

 :thumbsup:  

Bob.